A comparative study was carried out to explore carbon monoxide total columnar amount (CO TC) in background and polluted atmosphere, including the stations of ZSS (Zvenigorod), ZOTTO (Central Siberia), Peterhof, Beijing, and Moscow, during 1998-2014, on the basis of ground- and satellite-based spectroscopic measurements. Interannual variations of CO TC in different regions of Eurasia were obtained from ground-based spectroscopic observations, combined with satellite data from the sensors MOPITT (2001-14), AIRS (2003-14), and IASI MetOp-A (2010-13). A decreasing trend in CO TC (1998-2014) was found at the urban site of Beijing, where CO TC decreased by 1.14% 0.87% yr-1. Meanwhile, at the Moscow site, CO TC decreased remarkably by 3.73% 0.39% yr-1. In the background regions (ZSS, ZOTTO, Peterhof), the reduction was 0.9%-1.7% yr-1 during the same period. Based on the AIRSv6 satellite data for the period 2003-14, a slight decrease (0.4%-0.6% yr-1) of CO TC was detected over the midlatitudes of Eurasia, while a reduction of 0.9%-1.2% yr-1 was found in Southeast Asia. The degree of correlation between the CO TC derived from satellite products (MOPITTv6 Joint, AIRSv6 and IASI MetOp-A) and ground-based measurements was calculated, revealing significant correlation in unpolluted regions. While in polluted areas, IASI MetOp-A and AIRSv6 data underestimated CO TC by a factor of 1.5-2.8. On average, the correlation coefficient between ground- and satellite-based data increased significantly for cases with PBL heights greater than 500 m.

Fig. 1 Annual CO TC in autumn at the (a) background sites of Zvenigorod and Peterhof (15 September to 30 November) and (b) urban sites of Moscow (15 September to 30 November) and Beijing (1 October to 30 November). The missing results in some years is because of the statistically insufficient coverage of the measurements in the corresponding period (<5 days). The solid lines show the trend derived from average autumn values for 1998-2014, while the dashed lines represent 2007-2014 (black for Beijing and grey for Moscow in both plots). The trend estimates were obtained at the 95% confidence level, and the vertical lines mark the standard deviation in the determination of average values.

Fig. 3 Comparison of daily mean CO TC derived from the MOPITT v06 Joint data product with the data from the ground-based spectrometers (at ZSS and Beijing, 2010-14). The cases with impacts from natural fires are excluded.

Table 3. Intercomparison between the AIRS v6 satellite sensor and the two other satellite sensors (MOPITT v6 Joint and IASI MetOp-A). The slope (K) and correlation coefficient (R2) were calculated for average daily measurements of CO TC at ZSS, ZOTTO and Beijing, over 5°× 5° and 1°× 1° latitude-longitude domains.

Ground-based measurements (ZSS, Beijing, Peterhof)

All PBL heights

PBL heights ≥ 500 (400*) m

Sensor

N (days)

K

A

R2

N (days)

K

A

R2

Site; years

MOPITT

83

0.58

0.8

0.43

52

0.60

0.7

0.53

ZSS; 2010-14 (without fires)

AIRS

346

1.05

-0.1

0.66

245

0.91

0.2

0.70

IASI**

196

0.85

0.4

0.19**

139

1.30

-0.6

0.58

MOPITT

91

0.66

0.6

0.38

44

0.78

0.3

0.44

ZSS; 2010-14 (with fires)

AIRS

379

1.26

-0.5

0.61

278

1.26

-0.6

0.60

IASI

227

1.41

-0.6

0.35

170

1.88

-2.0

0.55

MOPITT

109

0.54

0.9

0.51

34

0.50

0.7

0.65

Peterhof; 2010-14

AIRS

382

1.07

-0.08

0.84

135

1.04

0.06

0.89

MOPITT

54

0.52

0.9

0.33

43

0.63

0.5

0.36

Beijing; 2010-14

AIRS

263

1.50

-0.8

0.32

224

1.55

-1.2

0.51

Table 4. Comparison between ground-based (ZSS, Peterhof, Beijing) and satellite-based (MOPITT, AIRS, IASI) measurements under different conditions of atmospheric mixing. The comparisons were made for the diurnal CO TC of ground- and satellite-based measurements averaged over the 1°× 1° latitude-longitude domain. The results are shown with and without PBL height selection.

Fig. 6 Relationship between the diurnal CO TC data from ground-based spectrometers, as well as AIRS v6 (domain 1°× 1°; sites ZSS and Beijing, 2010-14), and the PBL height: (a) for all days during the measurement period; (b) for days with PBL height ≥ 500 m.

Arshinov, M. Y.,Coauthors, 2014: Comparison between satellite spectrometric and aircraft measurements of the gaseous composition of the troposphere over Siberia during the forest fires of 2012. Izvestiya, Atmospheric and Oceanic Physics, 50, 916-928.

IPCC, 2001: Climate Change 2001: The Physical Science Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, UK and New York, USA.

28

IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, UK and New York, USA.

29

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, UK and New York, USA.

Rakitin, V. S.,Coauthors, 2017: Study of trends of total CO and CH4 contents over Eurasia through analysis of ground-based and satellite. Atmospheric and Oceanic Optics,30(6), 517-526.

38

Safronov A. N.,E. V. Fokeeva, V. S. Rakitin, L. N. Yurganov, and E. I. Grechko, 2012: Carbon monoxide emissions in summer 2010 in the central part of the Russian Plain and estimation of their uncertainties with the use of different land-cover maps. Izvestiya, Atmospheric and Oceanic Physics, 48, 925-940.

A comparative study was carried out to explore carbon monoxide total columnar amount (CO TC) in background and polluted atmosphere, including the stations of ZSS (Zvenigorod), ZOTTO (Central Siberia), Peterhof, Beijing, and Moscow, during 1998-2014, on the basis of ground- and satellite-based spectroscopic measurements. Interannual variations of CO TC in different regions of Eurasia were obtained from ground-based spectroscopic observations, combined with satellite data from the sensors MOPITT (2001-14), AIRS (2003-14), and IASI MetOp-A (2010-13). A decreasing trend in CO TC (1998-2014) was found at the urban site of Beijing, where CO TC decreased by 1.14% 0.87% yr-1. Meanwhile, at the Moscow site, CO TC decreased remarkably by 3.73% 0.39% yr-1. In the background regions (ZSS, ZOTTO, Peterhof), the reduction was 0.9%-1.7% yr-1 during the same period. Based on the AIRSv6 satellite data for the period 2003-14, a slight decrease (0.4%-0.6% yr-1) of CO TC was detected over the midlatitudes of Eurasia, while a reduction of 0.9%-1.2% yr-1 was found in Southeast Asia. The degree of correlation between the CO TC derived from satellite products (MOPITTv6 Joint, AIRSv6 and IASI MetOp-A) and ground-based measurements was calculated, revealing significant correlation in unpolluted regions. While in polluted areas, IASI MetOp-A and AIRSv6 data underestimated CO TC by a factor of 1.5-2.8. On average, the correlation coefficient between ground- and satellite-based data increased significantly for cases with PBL heights greater than 500 m.

IPCC, 2001: Climate Change 2001: The Physical Science Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, UK and New York, USA.

28

IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, UK and New York, USA.

29

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, UK and New York, USA.